On Wed, 20 Nov 2024 12:47:19 +0100
Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxx> wrote:
Long story short: it fails at kbuffer_load_subbuffer() call in
read_cpu_pages().
I added printf in the kbuffer helpers in libevent, and it finishes at:
__read_long_4: call read_4 at 0x600230c2
__read_4_sw: ptr=0x8044e2ac
static unsigned int __read_4_sw(void *ptr)
{
printf("%s: ptr=%p, value: %08x\n", __func__, ptr, *(unsigned int *)ptr);
unsigned int data = *(unsigned int *)ptr;
printf("%s: data=%08x\n", __func__, data);
return swap_4(data);
}
As soon as ptr is dereferenced, the segfault appears.
ptr should be ok though, as the address is valid afaik...
But you don't know what ptr it failed on, right?
If dereferencing a pointer will crash, the below line:
printf("%s: ptr=%p, value: %08x\n", __func__, ptr, *(unsigned int *)ptr);
Will crash before printing, because you are dereferencing ptr. Perhaps you
should change this to:
printf("%s: ptr=%p\n" value: %08x\n", __func__, ptr);
printf(" value: %08x\n", *(unsigned int *)ptr);
And that way you will see what 'ptr' is before the crash. Or did you do
that already?
-- Steve
I must say that now I am stuck :-(.
